Wind energy systems have gained more and more importance as a source of energy in recent years. As areas suitable for their economical operation are relatively scarce in a number of countries, a growing number of wind energy systems are located close to populated areas. As the running of wind turbines in wind energy systems causes noise, this leads to various problems such as resistance from neighborhoods and the like. A variety of factors contribute to the overall noise emission of such systems such as machinery noise emissions (of tonal nature) and aerodynamic noise emissions (more broad in nature).
Methods for reducing the noise emissions of wind energy systems have long been discussed. For example, it has been proposed to reduce aerodynamic noise caused by the blades through a speed/torque control of the system in order to keep turbine speed low during certain time intervals, e.g., during night time.
It is well established that in order to limit the noise generated by a wind turbine blade, the maximum tip speed at which the blades rotate can be reduced. The limitation of the tip speed requires a reduction in the rated power to limit the torque generated in the drive train of the turbine. This reduces the annual energy yield of the turbine.
What is needed is a method and system of limiting the noise generated by a wind turbine with reduced or eliminated reduction in tip speed.